Spin qubit based on the nitrogen-vacancy center analog in a diamond-like compound C3BN

At a Glance

Metadata	Details
Publication Date	2021-12-09
Journal	Journal of Applied Physics
Authors	Duo Wang, Lei Liu, Houlong Zhuang
Institutions	Arizona State University
Citations	8
Analysis	Full AI Review Included

Technical Analysis and Documentation: C₃BN Spin Qubit Host

Executive Summary

This research validates the potential of the Boron-Vacancy (V_B^-1) defect in the diamond-like compound C₃BN as a novel, scalable solid-state spin qubit host, offering significant advantages over traditional diamond Nitrogen-Vacancy (NV⁻) centers.

NV Analog Validation: DFT calculations confirm that the C₃BN V_B^-1 defect possesses all critical properties required for a robust spin qubit, including a wide band gap (3.75 eV), negligible spin-orbit coupling (SOC), and a stable paramagnetic triplet ground state (total spin 1).
Telecom Advantage: The predicted Zero-Phonon Line (ZPL) energies (1.104 eV and 1.504 eV) correspond to wavelengths (1123 nm and 824 nm) significantly closer to the ideal telecommunication O-band (1310 nm) and C-band (1550 nm).
Reduced Optical Loss: This shift to longer wavelengths is critical for minimizing optical loss in fiber-optic quantum networks, positioning C₃BN as a superior material for long-distance quantum communication.
Scalability & Compatibility: C₃BN belongs to the A₃XY family of compounds, which are compatible with existing Group IV semiconductor processing techniques (Si, Ge), promising highly scalable quantum device fabrication.
Quantum Register Potential: Computed hyperfine interactions are comparable to or stronger than those in diamond, suggesting C₃BN can effectively host multi-qubit registers for quantum error correction and entanglement distillation.
6CCVD Relevance: As the global leader in MPCVD diamond, 6CCVD provides the essential high-purity Single Crystal Diamond (SCD) benchmark material and the large-area Polycrystalline Diamond (PCD) platforms required for the synthesis and integration of these next-generation diamond-like qubit hosts.

Technical Specifications

Parameter	Value	Unit	Context
C₃BN Band Gap (Indirect)	3.75	eV	Calculated using SCAN functional
Diamond Band Gap (Indirect)	4.55	eV	Calculated using SCAN functional
C₃BN NV Analog Stability Range	1.52 to 3.26	eV	Fermi energy range for stable q = -1 state
C₃BN ZPL Energy (Case 1)	1.104	eV	Corresponds to 1123 nm wavelength
C₃BN ZPL Energy (Case 2)	1.504	eV	Corresponds to 824 nm wavelength
Diamond ZPL Energy (SCAN)	1.988	eV	Benchmark for NV center (Case 1)
C₃BN Lattice Parameters (a, b, c)	5.669, 5.670, 3.595	Å	Optimized monoclinic Bravais lattice
C₃BN Dielectric Constant (ε_bb)	5.75	-	Highest component, due to B-N polar bonds
Diamond Dielectric Constant	5.50	-	Consistent with experimental 5.68
C₁ Hyperfine Tensor (C₃BN, A_zz)	263.850	MHz	Strongest hyperfine interaction (C₁ atom)
C₃BN Spin Moment	1	Bohr magneton	Paramagnetic triplet ground state

Key Methodologies

The theoretical analysis relied on advanced Density Functional Theory (DFT) simulations to predict the electronic and structural properties of the C₃BN NV analog.

Computational Framework: All calculations were performed using the Vienna Ab initio Simulation Package (VASP) based on Density Functional Theory (DFT).
Functional Selection: The Strongly Constrained and Appropriately Normed (SCAN) semilocal density functional was employed for exchange-correlation interactions, chosen for its accuracy in describing band gaps and defect localization.
Potential Method: The Projector Augmented-Wave (PAW) method was used, defining valence electrons for C (2s²2p²), B (2s²2p¹), and N (2s²2p³).
Energy Cutoff: A plane waves cutoff kinetic energy of 400 eV was consistently applied across all VASP calculations.
Geometry Optimization: Atomic coordinates and lattice parameters were fully optimized until the force threshold reached 0.01 eV.
Defect Simulation: The C₃BN NV analog (V_B^-1) was simulated using a 2 × 2 × 3 supercell (240 atoms) derived from the optimized 20-atom cell, involving the removal of one B atom and the addition of an extra electron (q = -1).
Optical Property Prediction: Zero-Phonon Line (ZPL) energies, Stokes (S), and Anti-Stokes (AS) shifts were extracted from potential energy curves using constrained DFT and the Frank-Condon approximation.
Hyperfine Structure: Hyperfine tensors, including Fermi contact and dipole-dipole coupling terms, were calculated using gyromagnetic ratios for ¹³C, ¹⁴N, and ¹¹B isotopes to assess quantum register potential.

6CCVD Solutions & Capabilities

This research highlights the critical role of wide-band-gap, diamond-like materials in advancing solid-state quantum technology. 6CCVD is uniquely positioned to support the experimental realization and integration of C₃BN and other A₃XY compounds by providing world-class diamond materials and advanced fabrication services.

Research Requirement/Challenge	6CCVD Solution & Capability	Technical Advantage
NV Center Benchmark & Replication	Optical Grade Single Crystal Diamond (SCD)	Provides ultra-high purity SCD plates (0.1µm to 500µm thick) with surface roughness Ra < 1nm. Essential for establishing the baseline performance of the standard NV⁻ center against novel analogs like C₃BN.
Scalable Integration Platform	Large-Area Polycrystalline Diamond (PCD)	Offers custom PCD wafers up to 125mm diameter. This inch-size capability is crucial for integrating novel A₃XY compounds (compatible with semiconductor processing) onto robust, thermally managed diamond platforms.
Defect Engineering & Doping	Custom Boron-Doped Diamond (BDD)	6CCVD controls precise dopant incorporation during MPCVD growth. While the paper focuses on V_B, our BDD capability demonstrates the necessary control for creating specific, high-concentration defect centers in diamond-based materials.
Device Fabrication & Readout	In-House Metalization Services	We offer custom deposition of critical metals (Au, Pt, Pd, Ti, W, Cu). This allows researchers to immediately integrate electrodes and microwave control lines required for the optical pumping, spin initialization, and readout of the paramagnetic triplet state.
Advanced Material Synthesis	Custom MPCVD Substrates & Recipes	6CCVD’s expertise in high-pressure, high-temperature MPCVD growth provides the ideal environment for exploring the epitaxial growth of novel diamond-like materials, such as C₃BN, on optimized diamond or silicon substrates.
Global Supply Chain	Global Shipping (DDU/DDP)	Ensures rapid, reliable delivery of custom diamond materials worldwide, accelerating experimental timelines for international research teams.

Engineering Support

6CCVD’s in-house team of PhD material scientists specializes in wide-band-gap semiconductor defect physics and MPCVD growth optimization. We offer authoritative consultation on material selection, surface preparation, and custom specifications necessary to replicate or extend this research into the experimental phase for solid-state spin qubit hosts.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

The nitrogen-vacancy (NV) center in diamond plays important roles in emerging quantum technologies. Currently available methods to fabricate the NV center often involve complex processes such as N implantation. By contrast, in a diamond-like compound C3BN, creating a boron (B) vacancy immediately leads to an NV-center analog. We use the strongly constrained and appropriately normed semilocal density functional—this functional leads to nearly the same zero-phonon line (ZPL) energy as the experiment and as obtained from the more time-consuming hybrid density functional calculations—to explore the potential of this NV-center analog as a novel spin qubit for applications in quantum information processing. We show that the NV-center analog in C3BN possesses many similar properties to the NV center in diamond including a wide bandgap, weak spin-orbit coupling, an energetically stable negatively charged state, a highly localized spin density, a paramagnetic triplet ground state, and strong hyperfine interactions, which are the properties that make the NV center in diamond stand out as a suitable quantum bit (qubit). We also predict that the NV-center analog in C3BN exhibits two ZPL energies that correspond to longer wavelengths close to the ideal telecommunication band for quantum communications. C3BN studied here represents only one example of A3XY (A: group IV element; X/Y: group III/V elements) compounds. We expect many other compounds of this family to have similar NV-center analogs with a wide range of ZPL energies and functional properties, promising to be the new hosts of qubits for quantum technology applications. Furthermore, A3XY compounds often contain group IV elements such as silicon and germanium, so they are compatible with sophisticated semiconductor processing techniques. Our work opens up ample opportunities toward scalable qubit host materials and novel quantum devices.

Tech Support

Original Source

DOI: https://doi.org/10.1063/5.0074320

References

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